摘要:
党川花岗岩基产于祁连与北秦岭造山带结合部位,由9个岩体组成,岩石普遍低Ga、Rb、Zr、高Th、Ta、Hf,富集重稀土元素。泥盆纪以来岩体显著富集Th、Hf而贫Rb、Co,稀土总量、LREE/ HREE及δEu等与北秦岭二长花岗岩相似,岩石地球化学显示其源岩成分、形成环境和成岩作用的相似性以及演化上的连续性和继承性。志留纪岩体则显著高Cr、Co、Nb和相对富Y,显著贫Ga、Rb、Zr,稀土总量、LREE/HREE及δEu参数既显著有别于本区泥盆纪以来各岩体,又明显区别于秦巴同期闪长岩类。综合分析,志留纪岩体是俯冲造山过程中形成的具有岛弧特色的闪长岩类,泥盆纪以来各岩体是本区造山后与大陆抬升作用或与大陆裂谷作用有关的壳源花岗岩类。
Abstract:
Located in the area of the Qilian and west Qinling orogenic belts,the Dangchuan granitic batholith is composed of 9 granitic intrusives. Geochemically,the batholith in general is poor in Ga,Rb, Zr and rich in Th,Ta,Hf and HREE. The Devonian and post-Devonian plutons are obviously rich in Th and Hf,but poor in Rb and Co. The FREE,LREE/HREE and δEu of these plutons are similar to the adamellitoids in the northern Qinling. The lithogeochemstry characteristics between all these plutons show an evident similarity in their sources,tectonic environments,and origin,and also continuity and inheritance in evolution. While the Silurian intrusives are obviously rich in Cr,Co,Nb and rich in Y,but poor in Ga,Rb,Zr,FREE, LREE/HREE and BEu. These Silurian intrusives are not only different from the Devonian ones but also different from the contemporaneous dioritoids in the Qinlin-Bashan areas. It has been agued that the Silurian intrusives are island arc dioritoids which were formed during subduction orogenesis,while the Devonian and post-Devonian plutons were derived from crustal sources related to that has relations to crustal uplift or continent rifting during post-orogenic period.
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